Sofa bed

ABSTRACT

A sofa bed includes a seat portion, a backrest portion, a seat portion connecting rod, a backrest portion connecting rod, and two armrest frames. The seat portion connecting rod and the backrest portion connecting rod are connected at a locking mechanism and are pivotable relative to each other and lockable relative to each other. The two armrest frames are provided at both ends of the seat portion and the backrest portion in the longitudinal direction. Each of the armrest frames is provided with a sliding groove that opens toward the backrest portion and the seat portion and partially extends in the transverse direction. A rear end of the sliding groove is positioned lower than a front end of the sliding groove. An angle formed between the seat portion and the backrest portion can be locked to improve the reliability of the operation. A switching operation is quickly and easily achieved by allowing ta pin to slide in the sliding groove in an extension direction having a transverse component and a vertical component

PRIORITY CLAIM

This application claims the benefit of Chinese Patent Application No.202110064263.9, filed Jan. 18, 2021, which is incorporated herein byreference.

FIELD

The present disclosure relates to the design of furniture, andspecifically to a sofa bed.

BACKGROUND

With incremental improvements of people's material well-being life, theneed of the consumer for household furniture presents a trend ofdiversification, wherein sofa beds already become a type of popularfurniture products. The conventional sofa beds have some drawbacks, suchas for example, the switching of the conventional sofa beds between twostates is not smooth enough, so that it is usually difficult for anoperator with less power to complete the switching individually; theconventional sofa beds might not be stable enough in the sofa state, andan angle between the seat and the backrest might be changed, whichaffects the degree of comfort; and the folding manner of theconventional sofa beds is single and thus cannot satisfy the user'svarious demands.

Therefore, it is desirable to provide a sofa bed to at least partiallysolve the above problems.

SUMMARY

A main object of the present invention is to provide a sofa bed which iseasily switchable between two in-use positions and easy to operate.Furthermore, in a predetermined switching procedure and a predetermineuse procedure, an angle between a seat portion and a backrest portioncan be locked to improve the reliability of the operation. In theswitching operation, by allowing a pin to slide in a sliding groove inan extension direction having a transverse component and a verticalcomponent, the burden of an user in operation can be lightened, and theswitching operation can be achieved quickly and easily. Furthermore, thesofa bed may be provided with a plurality of detachable elastic moduleswhich are simple to mount and convenient to operate. Thus, the user maymanually mount them to obtain a sofa bed having a better degree ofcomfort.

According to an aspect of the present invention, there is provided asofa bed, comprising:

a main body frame comprising a seat portion and a backrest portionarranged adjacent to each other, the seat portion and the backrestportion being configured to be folded or unfolded about a lockingmechanism, so that the main body frame is changed between a bedconfiguration and a sofa configuration; and

an armrest frame respectively disposed on both sides of the main bodyframe in a longitudinal direction, and connected to the main body framevia the locking mechanism, wherein each of the armrest frames is formedwith a slideway through which the movement of the locking mechanism isguided,

wherein, when the backrest portion and the seat portion are pivotalrelative to each other about the locking mechanism, the sofa bed isconfigured to lock the backrest portion relative to the seat portion ata predetermined angle, and allow the locking mechanism to drive the mainbody frame to displace while the locking mechanism being guided by theslideway in a locked state.

According to a preferable embodiment of the present invention, thelocking mechanism comprises:

a seat portion connecting rod attached to and extending along atransverse side edge of the seat portion;

a backrest portion connecting rod attached to a transverse side edge ofthe backrest portion on the same side as the transverse side edge of theseat portion and extending along the transverse side edge of thebackrest portion; and

a pivot shaft connecting the seat portion connecting rod with thebackrest portion connecting rod so that the backrest portion and theseat portion can pivot relative to each other.

According to another preferable embodiment of the present invention, themain body frame is configured to release the locking between the seatportion connecting rod and the backrest portion connecting rod when theseat portion arranged in the locked stated is operated to pivot towardsthe backrest portion.

According to a further preferable embodiment of the present invention,one of the seat portion connecting rod and the backrest portionconnecting rod is provided with a ratchet, and the other of the seatportion connecting rod and the backrest portion connecting rod isprovided with a pawl, wherein the ratchet and the pawl engage with eachother so that the backrest portion is locked at a predetermined anglewith respect to the seat portion.

According to a further preferable embodiment of the present invention,an outer edge of the ratchet is provided with a recessed portion that isrecessed inward in a radial direction of the ratchet, and the pawl isprovided with a protruding portion corresponding to the recessedportion, wherein the protruding portion is configured to enable theprotruding portion to engage the recessed portion when the backrestportion and the seat portion form the predetermined angle, therebylocking the backrest portion and the seat portion.

According to a further preferable embodiment of the present invention,both the seat portion and the backrest portion are formed as arectangular structure.

According to a further preferable embodiment of the present invention, aside edge of the seat portion extending in the longitudinal directionand a side edge of the backrest portion extending in the longitudinaldirection are arranged adjacent to each other.

According to a further preferable embodiment of the present invention,the main body frame is configured such that the backrest portion can belocked at a plurality of different predetermined angles relative to theseat portion.

According to a further preferable embodiment of the present invention,the main body frame further comprises a driven beam, one end of thedriven beam is pivotally connected to the armrest frame, and the otherend of the driven beam is pivotally connected to the backrest portion.

According to a further preferable embodiment of the present invention,the armrest frame comprises a substantially

-shaped armrest frame body (referred to as a “channel shape”) and areinforcing transverse beam connected between two legs of the armrestframe body, and the slideway is formed on the reinforcing transversebeam.

According to a further preferable embodiment of the present invention,the locking mechanism is provided with a pin extending toward theoutside of the main body frame, and the slideway is a sliding grooveformed on the reinforcing transverse beam, one end of the slideway ispositioned higher than the other end of the slideway, and the one end isopen toward an upper edge of the armrest frame so as to receive the pinof the locking mechanism.

According to another preferable embodiment of the present invention, thereinforcing transverse beam is provided with a sliding rod, and thelocking mechanism is provided with a sliding sleeve which is configuredto be sleeved on the sliding rod and slide along the sliding rod.

According to a further preferable embodiment of the present invention, asliding rod is provided under the reinforcing transverse beam, and thesliding rod and a lower edge of the reinforcing transverse beam jointlydefine the sliding groove.

According to a further preferable embodiment of the present invention, across section of the reinforcing transverse beam is in a shape of

, and an outer end of the pin is provided with a protrusion that canmating with the

shape.

According to a further preferable embodiment of the present invention,the sofa bed comprises a bottom supporting structure that is disposedunder the backrest portion and the seat portion and is fixedly connectedto the two armrest frames.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference may be made to preferred embodiments shown in the figures toenable better understanding of the above and other objects, features,advantages and functions of the present invention. The same or likereference numerals in the figures denote the same or like parts. Thoseskilled in the art should appreciate that the figures are intended toschematically illustrate the preferred embodiments of the presentinvention, and not intended to limit the scope of the present invention,and all parts shown in the figures are not drawn to scale.

FIG. 1 is a perspective schematic view of a main body frame of a sofabed according to a preferred embodiment of the present invention when itis arranged in a bed state;

FIG. 2 is a side view of the sofa bed shown in FIG. 1;

FIG. 3 is a perspective schematic view of the main body frame of FIG. 1in a sofa state;

FIG. 4 is a side view of the sofa bed shown in FIG. 3;

FIG. 5 is an exploded schematic view of a junction of a seat portion anda backrest portion in the present embodiment;

FIG. 6A-FIG. 6F are side views of the main body frame according to thepreferred embodiment, which sequentially show a process in which thesofa transitions from a first in-use state to a second in-use state, andthen return back to the first in-use state;

FIG. 7A shows a schematic diagram of a sliding groove in the preferredembodiment;

FIG. 7B-FIG. 7D are alternative implementations of the sliding grooveshown in FIG. 7A;

FIG. 7E is a cross-sectional view taken along line C-C indicated in FIG.7D, wherein hatching lines are omitted in FIG. 7E for a clearerillustration purpose:

FIG. 8 is a schematic diagram of an elastic module of a sofa bedaccording to a preferred embodiment of the present invention;

FIG. 9-FIG. 11 are schematic diagrams of a process in which an elasticmodule is mounted to the main body frame;

FIG. 12 is a schematic diagram after elastic modules are mounted on themain body frame;

FIG. 13 and FIG. 14 are respective schematic diagrams showing shapes ofa finished product of the sofa bed.

DETAILED DESCRIPTION OF EMBODIMENTS

Specific embodiments of the present prevention will now be described indetail with reference to the figures. What are described here are onlypreferred embodiments according to the present invention. Those skilledin the art can implement other embodiments of the present invention onthe basis of the preferred embodiments, and said other embodiments alsofall within the scope of the present invention.

The invention provides a sofa bed. FIG. 1-FIG. 7E show at least partialstructures according to some preferred embodiments of the presentinvention. First, it will be appreciated that “transverse direction” and“longitudinal direction” mentioned in the present invention refer toabsolute directions, and respectively two directions perpendicular toeach other in a horizontal plane, wherein the transverse direction isshown by X in the figures, and the longitudinal direction is shown by Yin the figures; “widthwise direction” and “lengthwise direction”mentioned in the present invention refer to relative directions relativeto a rectangle formed by a seat portion and a backrest portion, but thelengthwise direction always coincides with the longitudinal direction Y,the widthwise direction coincides with the transverse direction X onlywhen the seat portion and/or backrest portion are placed horizontally. Aheight direction mentioned in the context is an absolute verticaldirection and shown by Z in the figures.

FIG. 1-FIG. 14 show some preferred embodiments of the present invention.

Referring to FIG. 1 through FIG. 4, a sofa bed according to a preferredembodiment of the present application comprising a main body frame 100which includes a seat portion 4, a backrest portion 3, a seat portionconnecting rod 41, a backrest portion connecting rod 31, and two armrestframes 2. The seat portion 4 and the backrest portion 3 are both formedas a rectangular structure, which may be a rectangular frame structureor a rectangular plate-like structure. A longitudinal edge of the seatportion 4 and a longitudinal edge of the backrest portion 3 are buttedtogether.

The seat portion connecting rod 41 is fixed on a widthwise edge of theseat portion 4, the backrest portion connecting rod 31 is fixed on awidthwise edge of the backrest portion 3, and the seat portionconnecting rod 41 and the backrest connecting rod 31 are connectedtogether in a way that they are pivotable relative to each other. Whenthe seat portion connecting rod 41 and the backrest portion connectingrod 31 pivot relative to each other, an angle formed therebetweenincreases or decreases. It will be appreciated that the “angle”mentioned in the present invention refers to an angle less than or equalto 180°.

The two armrest frames 2 are provided at both ends of the seat portion 4and the backrest portion 3 in the longitudinal direction, and each ofthe armrest frames 2 is provided with a slideway that opens toward thebackrest portion 3 and the seat portion 4 and partially extends in thetransverse direction. In the present embodiment, the slideway is asliding groove 211, and a rear end 211 b of the sliding groove 211 ispositioned lower than a front end 211 a of the sliding groove 211.

The exploded schematic view of the pivotal connection of the seatportion 4 and the backrest portion 3 is shown in FIG. 5. Referring toFIG. 5, the seat portion connecting rod 41 and the backrest portionconnecting rod 31 are engaged with each other at a locking mechanism 34,and the locking mechanism 34 has a pin 341 protruding from a side facingthe armrest. The front end 211 a of the sliding groove 211 is providedwith an upward opening, so that the pin 341 can enter into the slidinggroove 211 from the front end 211 a of the sliding groove 211 and slidein the sliding groove 211. A special-shaped gear and a gear matchingclaw are provided at the locking mechanism 34, and they are respectivelydisposed on the seat portion connecting rod 41 and the backrest portionconnecting rod 31. The special-shaped gear is for example a ratchetwheel 342, wherein the edge of the ratchet 342 is provided with arecessed portion that is recessed in a radial direction of the ratchet342. The gear matching pawl is provided with a protruding portion thatmates with the recessed portion. The recessed portion and the protrudingportion are positioned such that when the backrest portion 3 and theseat portion 4 are located at a predetermined obtuse angle, theprotruding portion is embedded or inserted in the recessed portion toachieve locking. The seat portion 4 is provided with a seat portioninsertion sleeve 42 for accommodating the seat portion connecting rod41, and the backrest portion 3 is provided with a backrest portioninsertion sleeve 32 for accommodating the backrest portion connectingrod 31.

Furthermore, each armrest frame 2 includes an armrest frame body 22 anda reinforcing transverse beam 21, wherein the sliding groove 211 isdisposed on the reinforcing transverse beam 21, and an extensiondirection of the reinforcing transverse beam 21 coincides with that ofthe sliding groove 21, i.e., the rear end 211 b of the reinforcingtransverse beam 21 is also positioned lower than the front end 211 a ofthe reinforcing transverse beam 21. The armrest frame body 22 furtherincludes two upright columns extending in the vertical direction and abody transverse beam connected at the tops of the two upright columns.The reinforcing transverse beam is connected to the middle of the twoupright columns and is parallel to the body transverse beam.

In addition to the armrest frame 2, the supporting and fixing structureof the sofa bed further includes a bottom supporting structure 24 whichis disposed under the backrest portion 3 and the seat portion 4 and isfixedly connected to the two armrest frames 2. The bottom supportingstructure 24 includes for example a bottom supporting structurelongitudinal beam, a bottom supporting structure transverse beam 23 andlegs 25. The sofa bed further includes a driven beam 26, one end ofwhich is pivotally connected to the armrest frame 2, and the other endof which is pivotally connected to the backrest portion 3.

FIG. 6A-FIG. 6F show a process in which the main body frame 100 changesfrom a first in-use position (at which the sofa bed is used as a bed) toa second in-use position (at which the sofa bed is used as a sofa) andthen returns back to the first in-used position.

First, referring to FIG. 6A, when the main body frame 100 is located atthe first in-use position, the backrest portion 3 and the seat portion 4are both horizontal, and the angle formed therebetween is a straightangle. The angle formed between the backrest portion connecting rod 31and the seat portion connecting rod 41 is also substantially a straightangle, and the pivot axis of the locking mechanism 34 is substantiallylocated adjacent to the front end 211 a of the sliding groove 211. Atthis time, the backrest portion connecting rod 31 and the seat portionconnecting rod 41 are not locked, thereby allowing the seat portion 4 tobe operated to pivot toward a position where the angle between the seatportion 4 and the backrest portion 3 is reduced. The direction of thepivoting is shown by an arrow in FIG. 6A.

When it requires to adjust the main body frame 100 to the second in-useposition, the seat portion 4 can be pivoted in the direction shown bythe arrow in FIG. 6A, to a position shown in FIG. 6B. At the positionshown in FIG. 6B, the pivoting between the backrest portion connectingrod 31 and the seat portion connecting rod 41 is locked. Specifically,for example, the locking mechanism 34 may be provided with aspecial-shaped ratchet 342 and a special-shaped pawl which have shapesmatching to each other. The special-shaped ratchet 342 and thespecial-shaped pawl are shaped to snap fit together at the positionshown in FIG. 6B to prevent the seat portion 4 from further rotatingrelative to the backrest portion 3. At this time, the angle between theseat portion 4 and the backrest portion 3 is a, which is an obtuseangle. The “predetermined obtuse angle” mentioned in the presentinvention may be understood as a shown in FIG. 6B.

At this time, the pin 341 at the locking mechanism 34 can enter into thesliding groove 211 from the front end 211 a of the sliding groove 211.Then, as shown in FIG. 6C, the seat portion 4 may be pressed down alongan arc-shaped arrow, and meanwhile the pin 341 can drive the combinationof the backrest portion 3 and the seat portion 4 to slide in a directionindicated by a straight arrow in FIG. 6C. After this operation, thecombination of the backrest portion 3 and the seat portion 4 can reachthe second in-use position as shown in FIG. 6D.

In the structure shown in FIG. 6B through FIG. 6D, the backrest portionconnecting rod 31 and the seat portion connecting rod 41 are locked toeach other at the locking mechanism 34, and the angle between thebackrest portion 3 and the seat portion 4 is always α.

When it is required to change the main body frame 100 from the secondin-use position to the first in-use position, the seat portion 4 can bemanually operated to further pivot toward the backrest portion 3 in thedirection indicated by the arrow as shown in FIG. 6D. The action forexample can make the protruding portion of the pawl disengage from therecessed portion of the ratchet, thereby releasing the locking betweenthe seat portion connecting rod 41 and the backrest portion connectingrod 31.

Referring to FIG. 6E, after the seat portion 4 is pivoted in thedirection indicated by arrow A, the locking between the seat portionconnecting rod 41 and the backrest portion connecting rod 31 isreleased. After the unlocking, the pin 341 is slided in the slidinggroove 211 toward the front end 211 a in the direction indicated by thearrow B, thereby driving the backrest portion 3 and the seat portion 4to reach the position shown in FIG. 6F, so that the main body frame 100returns to the first in-use position.

FIG. 7A shows details of the sliding groove 211 in FIG. 1 through FIG.6F. In the FIG. 7A, the sliding groove 211 is a groove structure formedon the reinforcing transverse beam 21 itself of the armrest frame 2.FIG. 7B through FIG. 7D show some alternative embodiments of FIG. 7A.

In the embodiment shown in FIG. 7B, the reinforcing transverse beam 21 ais provided with a sliding rod 212, and a sliding sleeve 341 a isfixedly fixed at the locking mechanism of the backrest portionconnecting rod and the seat portion connecting rod to engage with andslide on the sliding rod 212.

In the embodiment shown in FIG. 7C, a sliding rod is disposed under thereinforcing transverse beam 21 b, the sliding rod and the lower edge ofthe reinforcing transverse beam 21 b jointly define a sliding groove213, and a pin 341 b fixedly disposed at the locking mechanism of thebackrest portion connecting rod and the seat portion connecting rod canengage with and slide in the sliding groove 213.

In the embodiment shown in FIG. 7D, the reinforcing transverse beam 21 cis a special-shaped beam whose cross section is shown in FIG. 7E.Referring to FIG. 7E, the cross-section of the reinforcing transversebeam 21 c is in a shape of

, and a pin 341 c is fixedly disposed at the locking mechanism of thebackrest portion connecting rod and the seat portion connecting rod,wherein a projection having a shape that can mate with the

shape is provided

at an outer end of the pin 341 c, and the projection can be adaptivelyreceived in the 1L shaped beam so that the pin 341 c can slide along thesliding groove 214 without disengaging from the sliding groove 214. Twostoppers ae provided in the

-shaped beam, wherein a front stopper 214 b can constitute the front endof the sliding groove 214, and a rear stopper 214 a can constitute therear end of the sliding groove 214.

In addition to the above structure, the sofa bed according to thepresent invention may further include a plurality of elastic modules.FIG. 8 shows an example of an elastic module. Referring to FIG. 8, eachof the elastic modules 200 includes a conical spring 110 and a springbracket 121 accommodating the conical spring. The spring bracket 121includes a base, an end cover 122 and one or more sets of flexiblestraps 123. The base includes a base of a spring mounting seat, and eachspring mounting seat has a spring fixing portion for fixing one end ofthe conical spring 110. The end cover 122 is arranged opposite to andcooperative with the corresponding spring mounting seat to hold theconical spring 110, wherein the end cover 122 abuts against the otherend of the conical spring 100 opposite to the end fixed in the springmounting seat. Each set of flexible straps 123 includes a plurality offlexible straps spaced apart and evenly arranged between a correspondingpair of spring mounting seat and end cap. When one conical spring 110 isretained between the corresponding pair of spring mounting seat and endcap 122, the flexible straps 123 are located outside the conical spring110. Alternatively, the sofa bed further includes a cover covering theconical springs.

Referring to FIG. 9 through FIG. 11, the main body frame is providedwith slide rails (including a transverse slide rail 400 and longitudinalslide rails 300) which are configured in a way that a plurality ofelastic modules 200 can be mounted on the main body frame from theoutside of the main body frame and slide to a predetermined mountingposition, so that a plurality of elastic modules 200 are closelyarranged on a side of the main body frame facing the user (as shown inFIG. 12).

Preferably, the conical spring is mounted in the spring bracket with apredetermined initial compression force.

For example, referring to FIG. 9, the plurality of slide rails includeslongitudinal slide rails 300, the longitudinal ends 301 of which areopen, so that the elastic modules 200 can be received. Alternatively,the plurality of slide rails includes transverse side rails 400 whosetransverse ends 401 are open so that the elastic modules 200 can bereceived.

Referring to FIG. 10 and FIG. 11, the plurality of slide rails include aplurality of longitudinal slide rails 300 extending in the longitudinaldirection and a transverse slide rail 400 extending in the transversedirection. The longitudinal slide rails and transverse slide railscommunicate at their intersections to facilitate the elastic modules 200to switch side rails. Specifically, the transverse slide rail 400 isdisposed in the middle of the longitudinal direction Y of the main bodyframe, and the transverse end 401 of the transverse slide rail 400 isopened to receive the elastic module 200 from the outside of the mainbody frame. The arrangement of the plurality of slide rails are designedsuch that the plurality of elastic modules 200 can enter the transverseslide rail 400 on the main body frame from the end of the main bodyframe, and switch to the longitudinal slide rails 300 at theintersection of the transverse slide rails 400 and the longitudinalslide rail 300.

In a state that a plurality of elastic modules 200 are closely arrangedon the side of the main body frame facing the user as shown in FIG. 12,an outer covering may be further provided on the elastic modules toobtain a sofa bed finished product as shown in FIG. 13 and FIG. 14. FIG.13 shows a configuration of the sofa bed finished product as a bed; FIG.14 shows a configuration of the sofa bed finished product as a sofa.

The above depictions of various embodiments of the present invention areprovided to those having ordinary skill in the art for depictionpurpose, and are not intended to exclude other embodiments from thepresent prevention or limit the present prevention to a single disclosedembodiment. As described above, various alternatives and modificationsof the present prevention will be apparent to those of ordinary skill inthe art. Accordingly, although some alternative embodiments have beendescribed in detail, those having ordinary skill in the art willunderstand or readily develop other embodiments. The prevention isintended to cover all alternatives, modifications and variations of thepresent prevention described herein, as well as other embodimentsfalling within the spirit and scope of the present prevention describedherein.

1. A sofa bed, comprising: a main body frame (100) comprising a seatportion (4) and a backrest portion (3) arranged adjacent to each other,the seat portion (4) and the backrest portion (3) being configured to befolded or unfolded about a locking mechanism (34), so that the main bodyframe (100) transitions between a bed configuration and a sofaconfiguration; and an armrest frame (2) respectively disposed on bothsides of the main body frame (100) in a longitudinal direction andconnected to the main body frame (100) by the locking mechanism (34),wherein each of the armrest frames (2) is formed with a slideway (211)so that the movement of the locking mechanism (34) is guided by theslideway (211), wherein, when the backrest portion (3) and the seatportion (4) pivot relative to each other about the locking mechanism(34), the sofa bed is configured to lock the backrest portion (3)relative to the seat portion (4) at a predetermined angle (α), allowingthe locking mechanism (34) to be guided by the slideway (211) n a lockedstate to drive the main body frame (100) to displace.
 2. The sofa bedaccording to claim 1, wherein the locking mechanism (34) comprises: aseat portion connecting rod (41) attached to and extending along atransverse side edge of the seat portion (4); a backrest portionconnecting rod (42) attached to a transverse side edge of the backrestportion (3) on the same side as the transverse side edge of the seatportion (4) and extending along the transverse side edge of the backrestportion (3); and a pivot shaft connecting the seat portion connectingrod (41) with the backrest portion connecting rod (42), so that thebackrest portion (3) and the seat portion (4) can pivot relative to eachother.
 3. The sofa bed according to claim 1, wherein the main body frame(100) is configured to release the locking between the seat portionconnecting rod (41) and the backrest portion connecting rod (31) whenthe seat portion (4) arranged in the locked stated is operated to pivottowards the backrest portion (3).
 4. The sofa bed according to claim 3,wherein one of the seat portion connecting rod (41) and the backrestportion connecting rod (31) is provided with a ratchet (342), the otherof the seat portion connecting rod (41) and the backrest portionconnecting rod (31) is provided with a pawl, and the ratchet (342) andthe pawl engage with each other so that the backrest portion (3) islocked at a predetermined angle (α) with respect to the seat portion(4).
 5. The sofa bed according to claim 4, wherein an outer edge of theratchet (342) is provided with a recessed portion that is recessedinward in a radial direction of the ratchet (342), the pawl is providedwith a protruding portion corresponding to the recessed portion, and theprotruding portion is configured to enable the protruding portion toengage with the recessed portion when the backrest portion (3) and theseat portion (4) form the predetermined angle (α), thereby locking thebackrest portion (3) and the seat portion (4).
 6. The sofa bed accordingto claim 1, wherein both the seat portion (4) and the backrest portion(3) are formed as a rectangular structure.
 7. The sofa bed according toclaim 6, wherein a side edge of the seat portion (4) extending in thelongitudinal direction and a side edge of the backrest portion (3)extending in the longitudinal direction are arranged adjacent to eachother.
 8. The sofa bed according to claim 1, wherein the main body frame(100) is configured such that the backrest portion (3) can be locked ata plurality of different predetermined angles relative to the seatportion (4).
 9. The sofa bed according to claim 1, wherein the main bodyframe (100) further comprises a driven beam (26), one end of which ispivotally connected to the armrest frame (2), and the other end of whichis pivotally connected to the backrest portion (3).
 10. The sofa bedaccording to claim 1, wherein the armrest frame (2) comprises asubstantially

-shaped armrest frame body (22) and a reinforcing transverse beam (21)connected between two legs of the armrest frame body (22), and whereinthe slideway (211) is formed on the reinforcing transverse beam (21).11. The sofa bed according to claim 10, wherein the locking mechanism isprovided with a pin (341) extending toward the outside of the main bodyframe (100), and the slideway (211) is a sliding groove formed on thereinforcing transverse beam, wherein one end (211 a) of the slideway ispositioned higher than the other end (211 b) of the slideway, and theone end (211 a) is opened toward an upper edge of the armrest frame (2)to receive the pin (341) of the locking mechanism (34).
 12. The sofa bedaccording to claim 10, wherein a sliding rod is provided on thereinforcing transverse beam, and the locking mechanism is provided witha sliding sleeve configured to journal on the sliding rod and slidealong the sliding rod.
 13. The sofa bed according to claim 10, wherein asliding rod is provided under the reinforcing transverse beam (21 b),and the sliding rod and a lower edge of the reinforcing transverse beamjointly define a sliding groove (213).
 14. The sofa bed according toclaim 10, wherein a cross section of the reinforcing transverse beam (21c) is in a shape of “

”, and an outer end of the pin (341 c) is provided with a protrusionhaving a shape that match with the “

” shape.
 15. The sofa bed according to claim 1, wherein the sofa bedcomprises a bottom supporting structure (24) that is disposed under thebackrest portion (3) and the seat portion (4) and is fixedly connectedto the two armrest frames (2).